Solid-state imaging element, imaging device, and control method of solid-state imaging element

ABSTRACT

An object is to reduce a circuit scale in a solid-state imaging element that detects an address event.The solid-state imaging element is provided with a plurality of photoelectric conversion elements, a signal supply unit, and a detection unit. In this solid-state imaging element, each of the plurality of photoelectric conversion elements photoelectrically converts incident light to generate a first electric signal. Furthermore, in the solid-state imaging element, the detection unit detects whether or not a change amount of the first electric signal of each of the plurality of photoelectric conversion elements exceeds a predetermined threshold and outputs a detection signal indicating a result of the detection result.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of application Ser. No.16/962,783, filed Jul. 16, 2020, which is a 371 National Stage Entry ofInternational Application No.: PCT/JP2019/001517, filed on Jan. 18,2019, which claims the benefit of Japanese Priority Patent ApplicationJP 2018-008850 filed Jan. 23, 2018, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present technology relates to a solid-state imaging element, animaging device, and a control method of a solid-state imaging element.More specifically, the present technology relates to a solid-stateimaging element that compares an amount of incident light with athreshold, an imaging device, and a control method of a solid-stateimaging element.

BACKGROUND ART

Conventionally, a synchronous solid-state imaging element that imagesimage data (frame) in synchronization with a synchronization signal suchas a vertical synchronization signal is used in an imaging device andthe like. With this general synchronous solid-state imaging element, theimage data may be obtained only at every synchronization signal cycle(for example, 1/60 second), so that it is difficult to cope with a casewhere higher-speed processing is requested in a field regarding traffic,robot and the like. Therefore, an asynchronous solid-state imagingelement is proposed in which a detection circuit that detects in realtime as an address event that a light amount of the pixel exceeds athreshold for each pixel address is provided for each pixel (refer to,for example, Patent Document 1). The solid-state imaging element thatdetects the address event for each pixel in this manner is referred toas a dynamic vision sensor (DVS).

CITATION LIST Patent Document

Patent Document 1: Japanese Unexamined Patent Publication No.2017-535999

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The asynchronous solid-state imaging element (that is, DVS) describedabove may generate data at a much higher speed than that with thesynchronous solid-state imaging element to output. For this reason, forexample, in a traffic field, processing of recognizing an image of aperson or an obstacle may be executed at a high speed to improve safety.However, a detection circuit of the address event has a larger number ofelements such as transistors than a pixel circuit in the synchronoustype, and there is a problem that, if such circuit is provided for eachpixel, a circuit scale increases as compared with the synchronous type.

The present technology is achieved in view of such a situation, and anobject thereof is to reduce the circuit scale in the solid-state imagingelement that detects the address event.

Solutions to Problems

The present technology is made to solve the above-described problem, anda first aspect thereof is a solid-state imaging element provided with aplurality of photoelectric conversion elements each of whichphotoelectrically converts incident light to generate a first electricsignal, and a detection unit that detects whether or not a change amountof the first electric signal of each of the plurality of photoelectricconversion elements exceeds a predetermined threshold and outputs adetection signal indicating a result of the detection, and a controlmethod thereof. This brings about an effect that the detection result ofdetecting whether or not the change amount of the electric signals fromthe plurality of photoelectric conversion elements exceeds the thresholdis output.

Furthermore, in the first aspect, a signal supply unit that supplies thefirst electric signal of each of the plurality of photoelectricconversion elements to a connection node according to a predeterminedcontrol signal may be further provided, in which the detection unit maydetect whether or not the change amount of the first electric signalsupplied to the connection node exceeds the predetermined threshold.This brings about an effect that the detection result of detectingwhether or not the change amount of the electric signal supplied to theconnection node by the signal supply unit exceeds the threshold isoutput.

Furthermore, in the first aspect, a pixel signal generation unit thatgenerates a pixel signal according to a second electric signal generatedby the photoelectric conversion element may be further provided, inwhich the signal supply unit may sequentially select the second electricsignal of each of the plurality of photoelectric conversion elements tosupply to the pixel signal generation unit in a case where the changeamount exceeds the predetermined threshold. This brings about an effectthat the pixel signals are sequentially generated in a case where thechange amount exceeds the threshold.

Furthermore, in the first aspect, the connection node may be connectedto N (N is an integer not smaller than 2) of the photoelectricconversion elements, and the pixel signal generation unit may generate asignal of a voltage corresponding to the second electric signal of anelement selected according to a selection signal out of M (M is aninteger smaller than N) of the photoelectric conversion elements as thepixel signal. This brings about an effect that it is detected thatwhether or not the change amount of the electric signals from the Nphotoelectric conversion elements exceeds the threshold, and the pixelsignal is generated from a photocurrent of the selected element out ofthe M photoelectric conversion elements.

Furthermore, in the first aspect, the pixel signal generation unit maybe provided with a reset transistor that initializes a floatingdiffusion layer, an amplification transistor that amplifies a signal ofa voltage of the floating diffusion layer, and a selection transistorthat outputs the amplified signal as the pixel signal according to aselection signal, in which the detection unit may be provided with aplurality of N-type transistors that converts the first electric signalinto a voltage signal of a logarithm of the first electric signal, and aP-type transistor that supplies a constant current to the plurality ofN-type transistors. This brings about an effect that the pixel signalgeneration unit in which the transistors are arranged and the detectionunit generate and detect the pixel signal.

Furthermore, in the first aspect, the plurality of photoelectricconversion elements may be arranged on a light reception chip, and thedetection unit and the pixel signal generation unit may be arranged on adetection chip stacked on the light reception chip. This brings about aneffect of increasing a light receiving area.

Furthermore, in the first aspect, the plurality of photoelectricconversion elements and the reset transistor may be arranged on a lightreception chip, and the detection unit, the amplification transistor,and the selection transistor may be arranged on a detection chip stackedon the light reception chip. This brings about an effect that a circuitscale of the detection chip is reduced.

Furthermore, in the first aspect, the plurality of photoelectricconversion elements, the reset transistor, and the plurality of N-typetransistors may be arranged on a light reception chip, and theamplification transistor, the selection transistor, and the P-typetransistor may be arranged on a detection chip stacked on the lightreception chip. This brings about an effect that a circuit scale of thedetection chip is reduced.

Furthermore, in the first aspect, the plurality of photoelectricconversion elements, the pixel signal generation unit, and the pluralityof N-type transistors may be arranged on a light reception chip, and theP-type transistor may be arranged on a detection chip stacked on thelight reception chip. This brings about an effect that a circuit scaleof the detection chip is reduced.

Furthermore, in the first aspect, a signal supply unit that supplies thefirst electric signal of each of the plurality of photoelectricconversion elements to a connection node according to a predeterminedcontrol signal may be further provided, in which the detection unit mayfurther output a pixel signal corresponding to the first electricsignal, the signal supply unit may sequentially select the firstelectric signal of each of the plurality of photoelectric conversionelements to supply to the connection node in a case where the changeamount exceeds the predetermined threshold, and the detection unit maybe provided with first and second N-type transistors that convert thefirst electric signal into a voltage signal of a logarithm of the firstelectric signal, and a P-type transistor that supplies a constantcurrent to the first and second N-type transistors. This brings about aneffect that the pixel signals are sequentially generated in a case wherethe change amount exceeds the threshold.

Furthermore, in the first aspect, an analog/digital converter thatconverts the pixel signal into a digital signal may be further provided,in which the plurality of photoelectric conversion elements, the signalsupply unit, and the first and second N-type transistors may be arrangedon a light reception chip, and the P-type transistor and at least a partof the analog/digital converter may be arranged on a detection chipstacked on the light reception chip. This brings about an effect that acircuit scale of the detection chip is reduced.

Furthermore, in the first aspect, the analog/digital converter may beprovided with a signal side transistor to which the pixel signal isinput, a reference side transistor to which a predetermined referencesignal is input, a constant current source connected to the signal sidetransistor and the reference side transistor, and a current mirrorcircuit that amplifies a difference between the pixel signal and thepredetermined reference signal to output, and the plurality ofphotoelectric conversion elements, the signal supply unit, the first andsecond N-type transistors, the signal side transistor, the referenceside transistor, and the constant current source may be arranged on alight reception chip, and the P-type transistor and the current mirrorcircuit may be arranged on a detection chip stacked on the lightreception chip. This brings about an effect that a circuit scale of thedetection chip is reduced.

Furthermore, in the first aspect, a connection node connected to thephotoelectric conversion element and the detection unit, and for each ofthe plurality of photoelectric conversion elements, a current/voltageconversion unit that converts a photocurrent into a voltage signal of alogarithm of the photocurrent, a buffer that corrects the voltage signalto output, a capacitor inserted between the buffer and the connectionnode, and a signal processing unit that supplies an electric signal ofeach of the plurality of photoelectric conversion elements to theconnection node through the current/voltage conversion unit, the buffer,and the capacitor according to a predetermined control signal may befurther provided, in which the electric signal may include thephotocurrent and the voltage signal. This brings about an effect thatthe voltage signal of the logarithm of the photocurrent is supplied tothe connection node.

Furthermore, in the first aspect, an analog/digital converter thatconverts a pixel signal into a digital signal may be further provided,in which each of a predetermined number of current/voltage conversionunits arranged in a predetermined direction may further generate asignal of a voltage corresponding to the photocurrent as the pixelsignal, and output the pixel signal to the analog/digital converter.This brings about an effect that the pixel signals of a predeterminednumber of pixels are sequentially converted into digital signals.

Furthermore, in the first aspect, an analog/digital converter thatconverts a pixel signal into a digital signal for each of the pluralityof photoelectric conversion elements may be further provided, in whicheach of current/voltage conversion units may further generate a signalof a voltage corresponding to the photocurrent as the pixel signal, andoutput the pixel signal to the analog/digital converter. This bringsabout an effect that the pixel signal is converted into the digitalsignal for each pixel.

Furthermore, a second aspect of the present technology is a solid-stateimaging element provided with a photoelectric conversion element thatphotoelectrically converts incident light to generate an electricsignal, a signal supply unit that supplies the electric signal to eithera connection node or a floating diffusion layer according to apredetermined control signal, a detection unit that detects whether ornot a change amount of the electric signal supplied to the connectionnode exceeds a predetermined threshold and outputs a detection signalindicating a result of the detection, and a pixel signal generation unitthat generates a voltage signal corresponding to the electric signalsupplied to the floating diffusion layer as a pixel signal. Therefore,the pixel signal is generated for each pixel, and it is detected whetheror not the change amount of the electric signal exceeds the threshold.

Furthermore, in the second aspect, the signal supply unit may include afirst transistor that supplies the electric signal to the connectionnode according to a predetermined control signal, and a secondtransistor that supplies the electric signal to a floating diffusionlayer according to a predetermined control signal, the pixel signalgeneration unit may be arranged in each of a plurality of pixels, andthe first transistor and the detection unit may be arranged in a pixelbeing a detection target out of the plurality of pixels. This bringsabout an effect of reducing a circuit scale.

Furthermore, a third aspect of the present technology is an imagingdevice provided with a plurality of photoelectric conversion elementseach of which photoelectrically converts incident light to generate anelectric signal, a signal supply unit that supplies the electric signalof each of the plurality of photoelectric conversion elements to aconnection node according to a predetermined control signal, a detectionunit that detects whether or not a change amount of the electric signalsupplied to the connection node exceeds a predetermined threshold andoutputs a detection signal indicating a result of the detection, and arecording unit that records the detection signal. This brings about aneffect that the detection result of detecting whether or not the changeamount of the electric signals from the plurality of photoelectricconversion elements exceeds the threshold is recorded.

Furthermore, a fourth aspect of the present technology is a solid-stateimaging element provided with a first photoelectric conversion elementthat generates a first electric signal, a second photoelectricconversion element that generates a second electric signal, a detectionunit that detects whether or not at least any one of a change amount ofthe first electric signal or a change amount of the second electricsignal exceeds a predetermined threshold to output a detection signalindicating a result of the detection, and a connection node connected tothe first photoelectric conversion element, the second photoelectricconversion element, and the detection unit. This brings about an effectthat the detection result of whether or not the change amount of theelectric signal from any one of the plurality of photoelectricconversion elements exceeds the threshold is output.

Furthermore, in the fourth aspect, a first transistor that supplies thefirst electric signal to the connection node according to a firstcontrol signal, and a second transistor that supplies the secondelectric signal to the connection node according to a second controlsignal may be further provided, in which the detection unit may detectwhether or not a change amount of either the first or second electricsignal supplied to the connection node exceeds the predeterminedthreshold. This brings about an effect that the detection result ofdetecting whether or not the change amount of the electric signalsupplied to the connection node by the signal supply unit exceeds thethreshold is output.

Furthermore, in the fourth aspect, a pixel signal generating unit thatgenerates a first pixel signal according to a third electric signalgenerated by the first photoelectric conversion element and generates asecond pixel signal according to a fourth electric signal generated bythe second photoelectric conversion element, a third transistorconnected to the first photoelectric conversion element and the pixelsignal generating unit, and a fourth transistor connected to the secondphotoelectric conversion element and the pixel signal generating unitmay be further provided, in which the third transistor may supply thethird electric signal to the pixel signal generating unit in a casewhere the change amount of the first electric signal exceeds thepredetermined threshold, and the fourth transistor may supply the fourthelectric signal to the pixel signal generating unit in a case where thechange amount of the second electric signal exceeds the predeterminedthreshold. This brings about an effect that the pixel signals aresequentially generated in a case where the change amount exceeds thethreshold.

Furthermore, in the fourth aspect, the pixel signal generating unit mayinclude a first pixel signal generation unit that generates a firstpixel signal according to the third electric signal generated by thefirst photoelectric conversion element, and a second pixel signalgeneration unit that generates a second pixel signal according to thefourth electric signal generated by the second photoelectric conversionelement, in which the third transistor may supply the third electricsignal to the first pixel signal generation unit in a case where thechange amount of the first electric signal exceeds the predeterminedthreshold, and the fourth transistor may supply the fourth electricsignal to the second pixel signal generation unit in a case where thechange amount of the second electric signal exceeds the predeterminedthreshold. This brings about an effect that the pixel signals aresequentially generated in a case where the change amount exceeds thethreshold.

Furthermore, in the fourth aspect, a third photoelectric conversionelement that generates a fifth electric signal and a sixth electricsignal, a fifth transistor that supplies an electric signal of the fifthphotoelectric conversion element to the connection node according to athird control signal, and a second pixel signal generating unit thatgenerates a third pixel signal according to the sixth electric signalmay be further provided, in which the sixth transistor may supply thesixth electric signal to the second pixel signal generating unit in acase where a change amount of the fifth electric signal exceeds thepredetermined threshold. This brings about an effect that the pixelsignals are sequentially generated by the plurality of pixel signalgenerating units.

Furthermore, in the fourth aspect, the pixel signal generating unit maybe provided with a reset transistor that initializes a floatingdiffusion layer, an amplification transistor that amplifies a signal ofa voltage of the floating diffusion layer, and a selection transistorthat outputs the amplified signal as the first or second pixel signalaccording to a selection signal, and the detection unit may be providedwith a plurality of N-type transistors that converts a photocurrent intoa voltage signal of a logarithm of the photocurrent, and a P-typetransistor that supplies a constant current to the plurality of N-typetransistors. This brings about an effect that the pixel signals aresequentially generated in a case where the change amount exceeds thethreshold.

Furthermore, in the fourth aspect, the first electric signal may includea first photocurrent, and the second electric signal may include asecond photocurrent, a connection node connected to the firstphotoelectric conversion element, the second photoelectric conversionelement, and the detection unit, a first current/voltage conversion unitthat converts at least one of the first photocurrent or the secondphotocurrent into a voltage signal of a logarithm of the photocurrent, abuffer that corrects the voltage signal to output, a capacitor insertedbetween the buffer and the connection node, and a signal processing unitthat supplies at least one of the first electric signal or the secondelectric signal to the connection node through the current/voltageconversion unit, the buffer, and the capacitor according to apredetermined control signal may be further provided, in which the firstphotoelectric conversion element may generate the first photocurrent,and the second photoelectric conversion element may generate the secondphotocurrent. This brings about an effect that the voltage signal of thelogarithm of the photocurrent is supplied to the connection node.

Furthermore, in the fourth aspect, an analog/digital converter connectedto the first current/voltage conversion unit and the secondcurrent/voltage conversion unit may be further provided, in which thefirst current/voltage conversion unit may further generate a signal of avoltage corresponding to the first photocurrent as a first pixel signal,and output the first pixel signal to the analog/digital converter, andthe second current/voltage conversion unit may further generate a signalof a voltage corresponding to the second photocurrent as a second pixelsignal, and output the second pixel signal to the analog/digitalconverter. This brings about an effect that the pixel signals of apredetermined number of pixels are sequentially converted into digitalsignals.

Furthermore, in the fourth aspect, a first analog/digital converter thatconverts a first pixel signal into a first digital signal, and a secondanalog/digital converter that converts a second pixel signal into asecond digital signal may be further provided, in which the firstcurrent/voltage conversion unit may further generate a signal of avoltage corresponding to the first photocurrent as the first pixelsignal, and outputs the first pixel signal to the first analog/digitalconverter, and the second current/voltage conversion unit may furthergenerate a signal of a voltage corresponding to the second photocurrentas the second pixel signal, and output the second pixel signal to thesecond analog/digital converter. This brings about an effect that thepixel signals of a predetermined number of pixels are sequentiallyconverted into digital signals.

Furthermore, a fifth aspect of the present technology is a solid-stateimaging element provided with a first photoelectric conversion elementthat photoelectrically converts incident light to generate a firstelectric signal and a second electric signal, a first signal supply unitthat supplies the first electric signal to a connection node accordingto a first control signal, a second signal supply unit that supplies thesecond electric signal to a first floating diffusion layer according toa second control signal, a detection unit that detects whether or not achange amount of the first electric signal supplied to the connectionnode exceeds a predetermined threshold and outputs a detection signalindicating a result of the detection, and a first pixel signalgeneration unit that generates a first pixel signal corresponding to thesecond electric signal supplied to the first floating diffusion layer,and a control method thereof. This brings about an effect that thedetection result of detecting whether or not the change amount of theelectric signal supplied to the connection node exceeds the threshold isoutput.

Furthermore, in the fifth aspect, a second photoelectric conversionelement that photoelectrically converts incident light to generate athird electric signal, a third transistor that supplies to a secondfloating diffusion layer according to a third control signal, and asecond pixel signal generation unit that generates a voltage signalcorresponding to the third electric signal supplied to the secondfloating diffusion layer as a second pixel signal may be furtherprovided. This brings about an effect that the pixel signals aresequentially generated in a case where the change amount exceeds thethreshold.

Furthermore, a sixth aspect of the present technology is an imagingdevice provided with a first photoelectric conversion element thatphotoelectrically converts incident light to generate a first electricsignal, a second photoelectric conversion element that photoelectricallyconverts the incident light to generate a second electric signal, afirst signal supply unit that supplies the first electric signal to aconnection node according to a first control signal, a second signalsupply unit that supplies the second electric signal to the connectionnode according to a second control signal, a detection unit that detectswhether or not a change amount of the electric signal supplied to theconnection node exceeds a predetermined threshold and outputs adetection signal indicating a result of the detection, and a recordingunit that records the detection signal. This brings about an effect thatthe detection result of detecting whether or not the change amount ofthe electric signals from the plurality of photoelectric conversionelements exceeds the threshold is recorded.

Furthermore, a seventh aspect of the present technology is a solid-stateimaging element provided with a first photoelectric conversion elementthat photoelectrically converts incident light to generate first andsecond electric signals, a second photoelectric conversion element thatphotoelectrically converts the incident light to generate third andfourth electric signals, a first detection unit that detects whether ornot a change amount of the first electric signal exceeds a predeterminedthreshold and outputs a detection signal indicating a result of thedetection, a second detection unit that detects whether or not a changeamount of the third electric signal exceeds a predetermined thresholdand outputs a detection signal indicating a result of the detection, afirst transistor that supplies the first electric signal to the firstdetection unit according to a first control signal, a second transistorthat supplies the third electric signal to the second detection unitaccording to a second control signal, a pixel signal generation unitthat generates a pixel signal corresponding to any one of the second orfourth pixel signal, a third transistor that supplies the secondelectric signal to the pixel signal generation unit according to a thirdcontrol signal, and a fourth transistor that supplies the fourthelectric signal to the pixel signal generation unit according to afourth control signal. This brings about an effect that the detectionresult of detecting whether or not the change amount of the electricsignals from the plurality of photoelectric conversion elements exceedsthe threshold is generated and the pixel signal is generated.

Effects of the Invention

According to the present technology, in a solid-state imaging elementthat detects an address event, an excellent effect that a circuit scalemay be reduced may be obtained. Note that, the effects are notnecessarily limited to the effects herein described and may be theeffects described in the present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration example of animaging device in a first embodiment of the present technology.

FIG. 2 is a view illustrating an example of a stacking structure of asolid-state imaging element in the first embodiment of the presenttechnology.

FIG. 3 is a block diagram illustrating a configuration example of thesolid-state imaging element in the first embodiment of the presenttechnology.

FIG. 4 is a block diagram illustrating a configuration example of apixel array unit in the first embodiment of the present technology.

FIG. 5 is a circuit diagram illustrating a configuration example of apixel block in the first embodiment of the present technology.

FIG. 6 is a block diagram illustrating a configuration example of anaddress event detection unit in the first embodiment of the presenttechnology.

FIG. 7 is a circuit diagram illustrating a configuration example of acurrent/voltage conversion unit in the first embodiment of the presenttechnology.

FIG. 8 is a circuit diagram illustrating a configuration example of asubtractor and a quantizer in the first embodiment of the presenttechnology.

FIG. 9 is a block diagram illustrating a configuration example of acolumn analog-to-digital converter (ADC) in the first embodiment of thepresent technology.

FIG. 10 is a timing chart illustrating an example of an operation of thesolid-state imaging element in the first embodiment of the presenttechnology.

FIG. 11 is a flowchart illustrating an example of an operation of thesolid-state imaging element in the first embodiment of the presenttechnology.

FIG. 12 is a circuit diagram illustrating a configuration example of apixel block in a first variation of the first embodiment of the presenttechnology.

FIG. 13 is a circuit diagram illustrating a configuration example of apixel block in a second variation of the first embodiment of the presenttechnology.

FIG. 14 is a circuit diagram illustrating a configuration example of apixel block in a third variation of the first embodiment of the presenttechnology.

FIG. 15 is a block diagram illustrating a configuration example of apixel array unit in a second embodiment of the present technology.

FIG. 16 is a circuit diagram illustrating a configuration example of alight reception unit in the second embodiment of the present technology.

FIG. 17 is a circuit diagram illustrating a configuration example of alight reception unit in which a transfer transistor is reduced in thesecond embodiment of the present technology.

FIG. 18 is a circuit diagram illustrating a configuration example of acurrent/voltage conversion unit in the second embodiment of the presenttechnology.

FIG. 19 is a timing chart illustrating an example of an operation of asolid-state imaging element in the second embodiment of the presenttechnology.

FIG. 20 is a circuit diagram illustrating a configuration example of acurrent/voltage conversion unit in a variation of the second embodimentof the present technology.

FIG. 21 is a circuit diagram illustrating a configuration example of anADC in the variation of the second embodiment of the present technology.

FIG. 22 is a block diagram illustrating a configuration example of apixel array unit in a third embodiment of the present technology.

FIG. 23 is a circuit diagram illustrating a configuration example of alight reception unit in the third embodiment of the present technology.

FIG. 24 is a block diagram illustrating a configuration example of anaddress event detection unit in the third embodiment of the presenttechnology.

FIG. 25 is a circuit diagram illustrating a configuration example of alight reception unit in a variation of the third embodiment of thepresent technology.

FIG. 26 is a block diagram illustrating a configuration example of apixel array unit in a fourth embodiment of the present technology.

FIG. 27 is a block diagram illustrating a configuration example of apixel array unit in a variation of the fourth embodiment of the presenttechnology.

FIG. 28 is a circuit diagram illustrating a configuration example of anormal pixel in a variation of the fourth embodiment of the presenttechnology.

FIG. 29 is a block diagram illustrating a configuration example of apixel array unit in a fifth embodiment of the present technology.

FIG. 30 is a block diagram illustrating a configuration example of apixel block in the fifth embodiment of the present technology.

FIG. 31 is a block diagram illustrating a configuration example of apixel block in a sixth embodiment of the present technology.

FIG. 32 is a block diagram illustrating a schematic configurationexample of a vehicle control system.

FIG. 33 is an explanatory view illustrating an example of aninstallation position of an imaging unit.

MODE FOR CARRYING OUT THE INVENTION

Modes for carrying out the present technology (hereinafter, referred toas embodiments) are hereinafter described. The description is given inthe following order.

1. First Embodiment (example in which a plurality of pixels shares anaddress event detection unit)

2. Second Embodiment (example in which pixel signal generation units arereduced and a plurality of pixels shares an address event detectionunit)

3. Third Embodiment (example in which a plurality of pixels eachprovided with a capacitor shares an address event detection unit)

4. Fourth Embodiment (example in which an address event detection unitis arranged for each pixel)

5. Fifth Embodiment (example in which the number of pixels sharing animage signal generation unit is smaller than the number of pixelssharing an address event detection unit)

6. Application Example to Mobile Body

1. First Embodiment

[Configuration Example of Imaging Device]

FIG. 1 is a block diagram illustrating a configuration example of animaging device 100 in a first embodiment of the present technology. Theimaging device 100 is provided with an imaging lens 110, a solid-stateimaging element 200, a recording unit 120, and a control unit 130. Asthe imaging device 100, a camera mounted on an industrial robot, anin-vehicle camera and the like are assumed.

The imaging lens 110 condenses incident light and guides the same to thesolid-state imaging element 200. The solid-state imaging element 200photoelectrically converts the incident light to image image data. Thesolid-state imaging element 200 executes predetermined signal processingsuch as image recognition processing on the imaged image data, andoutputs data indicating a processing result and a detection signal of anaddress event to the recording unit 120 via a signal line 209. Agenerating method of the detection signal is described later.

The recording unit 120 records the data from the solid-state imagingelement 200. The control unit 130 controls the solid-state imagingelement 200 to image the image data.

[Configuration Example of Solid-state Imaging Element]

FIG. 2 is a view illustrating an example of a stacking structure of thesolid-state imaging element 200 in the first embodiment of the presenttechnology. The solid-state imaging element 200 is provided with adetection chip 202 and a light reception chip 201 stacked on thedetection chip 202. These chips are electrically connected to each othervia a connection unit such as a via. Note that, they may also beconnected to each other by Cu—Cu joint or a bump in addition to the via.

FIG. 3 is a block diagram illustrating a configuration example of thesolid-state imaging element 200 in the first embodiment of the presenttechnology. The solid-state imaging element 200 is provided with a drivecircuit 211, a signal processing unit 212, an arbiter 213, a column ADC220, and a pixel array unit 300.

In the pixel array unit 300, a plurality of pixels is arranged in atwo-dimensional lattice manner. Furthermore, the pixel array unit 300 isdivided into a plurality of pixel blocks each of which includes apredetermined number of pixels. Hereinafter, a set of pixels or pixelblocks arranged in a horizontal direction is referred to as a “row”, anda set of pixels or pixel blocks arranged in a direction perpendicular tothe row is referred to as a “column”.

Each of the pixels generates an analog signal of a voltage correspondingto a photocurrent as a pixel signal. Furthermore, each of the pixelblocks detects presence/absence of the address event depending onwhether or not a change amount of the photocurrent exceeds apredetermined threshold. Then, when the address event occurs, the pixelblock outputs a request to the arbiter.

The drive circuit 211 drives each of the pixels to allow the same tooutput the pixel signal to the column ADC 220.

The arbiter 213 arbitrates the request from each pixel block andtransmits a response to the pixel block on the basis of an arbitrationresult. The pixel block that receives the response supplies a detectionsignal indicating a detection result to the drive circuit 211 and thesignal processing unit 212.

The column ADC 220 converts, for each column of the pixel blocks, theanalog pixel signals from the column into digital signals. The columnADC 220 supplies the digital signals to the signal processing unit 212.

The signal processing unit 212 executes predetermined signal processingsuch as correlated double sampling (CDS) processing and imagerecognition processing on the digital signals from the column ADC 220.The signal processing unit 212 supplies data indicating a processingresult and the detection signal to the recording unit 120 via the signalline 209.

[Configuration Example of Pixel Array Unit]

FIG. 4 is a block diagram illustrating a configuration example of thepixel array unit 300 in the first embodiment of the present technology.The pixel array unit 300 is divided into a plurality of pixel blocks310. In each of the pixel blocks 310, a plurality of pixels is arrangedin I rows×J columns (I and J are integers).

Furthermore, the pixel block 310 is provided with a pixel signalgeneration unit 320, a plurality of light reception units 330 of Irows×J columns, and an address event detection unit 400. The pluralityof light reception units 330 in the pixel block 310 shares the pixelsignal generation unit 320 and the address event detection unit 400.Then, a circuit including the light reception unit 330 at certaincoordinates, the pixel signal generation unit 320, and the address eventdetection unit 400 serves as a pixel at the coordinates. Furthermore, avertical signal line VSL is arranged for each column of the pixel blocks310. When the number of columns of the pixel blocks 310 is set to m (mis an integer), m vertical signal lines VSL are arranged.

The light reception unit 330 photoelectrically converts the incidentlight to generate the photocurrent. The light reception unit 330supplies the photocurrent to either the pixel signal generation unit 320or the address event detection unit 400 under the control of the drivecircuit 211.

The pixel signal generation unit 320 generates a signal of the voltagecorresponding to the photocurrent as a pixel signal SIG. The pixelsignal generation unit 320 supplies the generated pixel signal SIG tothe column ADC 220 via the vertical signal line VSL.

The address event detection unit 400 detects the presence/absence of theaddress event on the basis of whether or not the change amount of thephotocurrent from each of the light reception units 330 exceeds apredetermined threshold. The address event includes, for example, anon-event indicating that the change amount exceeds an upper limitthreshold and an off-event indicating that the change amount falls belowa lower limit threshold. Furthermore, the detection signal of theaddress event includes, for example, one bit indicating a detectionresult of the on-event and one bit indicating a detection result of theoff-event. Note that, it is also possible that the address eventdetection unit 400 detects only the on-event.

When the address event occurs, the address event detection unit 400supplies a request for transmission of the detection signal to thearbiter 213. Then, upon receiving a response to the request from thearbiter 213, the address event detection unit 400 supplies the detectionsignal to the drive circuit 211 and the signal processing unit 212. Notethat, the address event detection unit 400 is an example of a detectionunit recited in claims.

[Configuration Example of Pixel Block]

FIG. 5 is a circuit diagram illustrating a configuration example of thepixel block 310 in the first embodiment of the present technology. Inthe pixel block 310, the pixel signal generation unit 320 is providedwith a reset transistor 321, an amplification transistor 322, aselection transistor 323, and a floating diffusion layer 324. Theplurality of light reception units 330 is commonly connected to theaddress event detection unit 400 via a connection node 340.

Furthermore, each of the light reception units 330 is provided with atransfer transistor 331, an overflow gate (OFG) transistor 332, and aphotoelectric conversion element 333. When the number of pixels in thepixel block 310 is set to N (N is an integer), N transfer transistors331, N OFG transistors 332, and N photoelectric conversion elements 333are arranged. A transfer signal TRGn is supplied to an n-th (n is aninteger from 1 to N) transfer transistor 331 in the pixel block 310 bythe drive circuit 211. A control signal OFGn is supplied to an n-th OFGtransistor 332 by the drive circuit 211.

Furthermore, as the reset transistor 321, the amplification transistor322, and the selection transistor 323, for example, N-typemetal-oxide-semiconductor (MOS) transistors are used. The N-type MOStransistors are similarly used for the transfer transistor 331 and theOFG transistor 332.

Furthermore, each of the photoelectric conversion elements 333 isarranged on the light reception chip 201. All the elements other thanthe photoelectric conversion element 333 are arranged on the detectionchip 202.

The photoelectric conversion element 333 photoelectrically converts theincident light to generate charge. The transfer transistor 331 transfersthe charge from the corresponding photoelectric conversion element 333to the floating diffusion layer 324 according to the transfer signalTRGn. The OFG transistor 332 supplies an electric signal generated bythe corresponding photoelectric conversion element 333 to the connectionnode 340 according to the control signal OFGn. Here, the suppliedelectric signal is the photocurrent including the charge. Note that, acircuit including the transfer transistor 331 and the OFG transistor 332of each pixel is an example of a signal supply unit recited in claims.

The floating diffusion layer 324 accumulates the charge and generates avoltage corresponding to an amount of the accumulated charge. The resettransistor 321 initializes the charge amount of the floating diffusionlayer 324 according to a reset signal from the drive circuit 211. Theamplification transistor 322 amplifies the voltage of the floatingdiffusion layer 324. The selection transistor 323 outputs a signal ofthe amplified voltage as the pixel signal SIG to the column ADC 220 viathe vertical signal line VSL according to a selection signal SEL fromthe drive circuit 211.

When being instructed by the control unit 130 to start detecting theaddress event, the drive circuit 211 drives the OFG transistors 332 ofall the pixels by the control signal OFGn to allow the same to supplythe photocurrent. Therefore, the address event detection unit 400 issupplied with a current that is the sum of the photocurrents of all thelight reception units 330 in the pixel block 310.

Then, when the address event is detected in a certain pixel block 310,the drive circuit 211 turns off all the OFG transistors 332 in thisblock to stop supplying the photocurrent to the address event detectionunit 400. Next, the drive circuit 211 sequentially drives the transfertransistors 331 by the transfer signal TRGn to transfer the charge tothe floating diffusion layer 324. Therefore, the pixel signals of theplurality of pixels in the pixel block 310 are sequentially output.

In this manner, the solid-state imaging element 200 outputs only thepixel signal of the pixel block 310 in which the address event isdetected to the column ADC 220. Therefore, it is possible to reducepower consumption of the solid-state imaging element 200 and aprocessing amount of the image processing as compared with a case wherethe pixel signals of all the pixels are output regardless of thepresence/absence of the address event.

Furthermore, since a plurality of pixels shares the address eventdetection unit 400, it is possible to reduce a circuit scale of thesolid-state imaging element 200 as compared with a case where theaddress event detection unit 400 is arranged for each pixel.

[Configuration Example of Address Event Detection Unit]

FIG. 6 is a block diagram illustrating a configuration example of theaddress event detection unit 400 in the first embodiment of the presenttechnology. The address event detection unit 400 is provided with acurrent/voltage conversion unit 410, a buffer 420, a subtractor 430, aquantizer 440, and a transfer unit 450.

The current/voltage conversion unit 410 converts the photocurrent fromthe corresponding light reception unit 330 into a voltage signal of itslogarithm. The current/voltage conversion unit 410 supplies the voltagesignal to the buffer 420.

The buffer 420 corrects the voltage signal from the current/voltageconversion unit 410. The buffer 420 outputs the corrected voltage signalto the subtractor 430.

The subtractor 430 lowers a level of the voltage signal from the buffer420 according to a row drive signal from the drive circuit 211. Thesubtractor 430 supplies the lowered voltage signal to the quantizer 440.

The quantizer 440 quantizes the voltage signal from the subtractor 430into a digital signal and outputs the same as the detection signal tothe transfer unit 450.

The transfer unit 450 transfers the detection signal from the quantizer440 to the signal processing unit 212 and the like. When the addressevent is detected, the transfer unit 450 supplies the request for thetransmission of the detection signal to the arbiter 213. Then, uponreceiving the response to the request from the arbiter 213, the transferunit 450 supplies the detection signal to the drive circuit 211 and thesignal processing unit 212.

[Configuration Example of Current/Voltage Conversion Unit]

FIG. 7 is a circuit diagram illustrating a configuration example of thecurrent/voltage conversion unit 410 in the first embodiment of thepresent technology. The current/voltage conversion unit 410 is providedwith N-type transistors 411 and 413 and a P-type transistor 412. Forexample, MOS transistors are used as these transistors.

A source and a drain of the N-type transistor 411 are connected to thelight reception unit 330 and a power supply terminal, respectively. TheP-type transistor 412 and the N-type transistor 413 are connected inseries between a power supply terminal and a ground terminal.Furthermore, a connection point between the P-type transistor 412 andthe N-type transistor 413 is connected to a gate of the N-typetransistor 411 and an input terminal of the buffer 420. Furthermore, apredetermined bias voltage Vbias is applied to a gate of the P-typetransistor 412.

Drains of the N-type transistors 411 and 413 are connected to a powersupply side, and such circuits are referred to as source followers. Thephotocurrent from the light reception unit 330 is converted into thevoltage signal of its logarithm by the two source followers connectedinto a loop. Furthermore, the P-type transistor 412 supplies a constantcurrent to the N-type transistor 413.

[Configuration Example of Subtractor and Quantizer]

FIG. 8 is a circuit diagram illustrating a configuration example of thesubtractor 430 and the quantizer 440 in the first embodiment of thepresent technology. The subtractor 430 is provided with capacitors 431and 433, an inverter 432, and a switch 434. Furthermore, the quantizer440 is provided with a comparator 441.

One end of the capacitor 431 is connected to an output terminal of thebuffer 420 and the other end thereof is connected to an input terminalof the inverter 432. The capacitor 433 is connected in parallel with theinverter 432. The switch 434 opens/closes a path connecting both ends ofthe capacitor 433 according to the row drive signal.

The inverter 432 inverts the voltage signal input via the capacitor 431.The inverter 432 outputs the inverted signal to a non-inverting inputterminal (+) of the comparator 441.

When the switch 434 is turned on, a voltage signal V_(init) is input toa buffer 420 side of the capacitor 431, and the opposite side becomes avirtual ground terminal. Potential of this virtual ground terminal isset to zero for convenience. At that time, potential Q_(init)accumulated in the capacitor 431 is expressed by a following expressionwhen capacitance of the capacitor 431 is set to C1. On the other hand,since both the ends of the capacitor 433 are short-circuited, theaccumulated charge thereof is zero.Q _(init) =C1×V _(init)   Expression 1

Next, considering a case where the switch 434 is turned off and thevoltage on the buffer 420 side of the capacitor 431 changes toV_(after), charge Q_(after) accumulated in the capacitor 431 isexpressed by a following expression.Q _(after) =C1×V _(after)   Expression 2

On the other hand, charge Q2 accumulated in the capacitor 433 isexpressed by a following expression when an output voltage is set toV_(out).Q2=−C2×V _(out)   Expression 3

At that time, a total charge amount of the capacitors 431 and 433 doesnot change, so that following expression holds.Q _(init) =Q _(after) +Q2   Expression 4

By substituting Expressions 1 to 3 into Expression 4 and transforming, afollowing expression is obtained.V _(out)=−(C1/C2)×(V _(after) −V _(init))  Expression 5

Expression 5 expresses a subtracting operation of the voltage signal,and a gain of a subtraction result is C1/C2. Since it is generallydesired to maximize the gain, it is preferable to design C1 larger andC2 smaller. On the other hand, if C2 is too small, kTC noise increases,and there is a possibility that a noise characteristic deteriorates, sothat a reduction in capacitance of C2 is limited to a range in which thenoise may be allowed. Furthermore, since the address event detectionunit 400 including the subtractor 430 is mounted for each pixel block,there is a limitation in area of the capacitance C1 and the capacitanceC2. In consideration of them, values of the capacitance C1 and thecapacitance C2 are determined.

The comparator 441 compares the voltage signal from the subtractor 430with a predetermined threshold voltage Vth applied to an inverting inputterminal (−). The comparator 441 outputs a signal indicating acomparison result to the transfer unit 450 as the detection signal.

Furthermore, a gain A of an entire address event detection unit 400described above is expressed by a following expression when a conversiongain of the current/voltage conversion unit 410 is set to CG_(log) and again of the buffer 420 is set to “1”.

[Mathematical Expression 1]

$\begin{matrix}{A = {{\frac{{{CG}_{\log} \cdot C}1}{C2}{\sum\limits_{n = 1}^{N}i_{photo}}} - n}} & {{Expression}6}\end{matrix}$

In the above expression, i_(photo_n) represents the photocurrent of then-th pixel, and its unit is, for example, ampere (A). N represents thenumber of pixels in the pixel block 310.

[Configuration Example of Column ADC]

FIG. 9 is a block diagram illustrating a configuration example of thecolumn ADC 220 in the first embodiment of the present technology. Thecolumn ADC 220 is provided with an ADC 230 for each column of the pixelblock 310. Furthermore, the column ADC 220 is provided with a referencesignal generation unit 231 and an output unit 232. The reference signalgeneration unit 231 generates a reference signal such as a ramp signaland supplies the same to each of the ADCs 230. A digital to analogconverter (DAC) and the like is used as the reference signal generationunit 231. The output unit 232 supplies the digital signal from the ADC230 to the signal processing unit 212.

The ADC 230 converts an analog pixel signal SIG supplied via thevertical signal line VSL into a digital signal. The ADC 230 is providedwith a comparator 231, a counter 232, a switch 233, and a memory 234.The comparator 231 compares the reference signal with the pixel signalSIG, and the counter 232 counts a count value over a period until acomparison result is inverted. The switch 233 supplies the count valueto the memory 234 and allows the same to hold the count value under thecontrol of a timing control circuit (not illustrated) and the like. Thememory 234 supplies a digital signal indicating the count value to theoutput unit 232 under the control of a horizontal drive unit (notillustrated) and the like. With this configuration, the pixel signal SIGis converted into a digital signal having a larger bit depth than thatof the detection signal. For example, if the detection signal is of twobits, the pixel signal is converted into the digital signal of three ormore bits (16 bits and the like). Note that, the ADC 230 is an exampleof an analog/digital converter recited in claims.

[Operation Example of Solid-State Imaging Element]

FIG. 10 is a timing chart illustrating an example of an operation of thesolid-state imaging element 200 in the first embodiment of the presenttechnology. At timing T0, when being instructed by the control unit 130to start detecting the address event, the drive circuit 211 sets all thecontrol signals OFGn to a high level to turn on the OFG transistors 332of all the pixels. Therefore, the sum of the photocurrents of all thepixels is supplied to the address event detection unit 400. On the otherhand, all the transfer signals TRGn are at a low level, and the transfertransistors 331 of all the pixels are in an off state.

Then, suppose that the address event detection unit 400 detects theaddress event and outputs a high-level detection signal at timing T1.Here, suppose that the detection signal is a one-bit signal indicatingthe detection result of the on-event.

Upon receiving the detection signal, the drive circuit 211 sets all thecontrol signals OFGn to a low level to stop supplying the photocurrentto the address event detection unit 400 at timing T2. Furthermore, thedrive circuit 211 sets the selection signal SEL to a high level and setsa reset signal RST to a high level over a certain pulse period toinitialize the floating diffusion layer 324. The pixel signal generationunit 320 outputs a voltage at the initialization as a reset level, andthe ADC 230 converts the reset level into a digital signal.

At timing T3 after the conversion of the reset level, the drive circuit211 supplies a high-level transfer signal TRG1 over a certain pulseperiod to allow a first pixel to output a voltage as a signal level. TheADC 230 converts the signal level into a digital signal. The signalprocessing unit 212 obtains a difference between the reset level and thesignal level as a net pixel signal. This processing is referred to asthe CDS processing.

At timing T4 after the conversion of the signal level, the drive circuit211 supplies a high-level transfer signal TRG2 over a certain pulseperiod to allow a second pixel to output a signal level. The signalprocessing unit 212 obtains a difference between the reset level and thesignal level as a net pixel signal. Thereafter, similar processing isexecuted, and the pixel signals of the respective pixels in the pixelblock 310 are sequentially output.

When all the pixel signals are output, the drive circuit 211 sets allthe control signals OFGn to the high level and turns on the OFGtransistors 332 of all the pixels.

FIG. 11 is a flowchart illustrating an example of the operation of thesolid-state imaging element 200 in the first embodiment of the presenttechnology. This operation starts, for example, when a predeterminedapplication for detecting the address event is executed.

Each of the pixel blocks 310 detects the presence/absence of the addressevent (step S901). The drive circuit 211 determines whether or not thereis the address event in any of the pixel blocks 310 (step S902). In acase where there is the address event (step S902: Yes), the drivecircuit 211 allows the respective pixels in the pixel block 310 in whichthe address event occurs to sequentially output the pixel signals (stepS903).

In a case where there is no address event (step S902: No) or after stepS903, the solid-state imaging element 200 repeats step S901 andsubsequent steps.

In this manner, according to the first embodiment of the presenttechnology, the address event detection unit 400 detects the changeamount of the photocurrent of each of the plurality of (N) photoelectricconversion elements 333 (pixels), so that it is possible to arrange oneaddress event detection unit 400 for every N pixels. By sharing oneaddress event detection unit 400 by N pixels in this manner, the circuitscale may be reduced as compared with the configuration in which theaddress event detection unit 400 is not shared but provided for eachpixel.

[First Variation]

In the above-described first embodiment, the elements other than thephotoelectric conversion element 333 are arranged on the detection chip202, but in this configuration, there is a possibility that the circuitscale of the detection chip 202 increases as the number of pixelsincreases. A solid-state imaging element 200 in a first variation of thefirst embodiment is different from that in the first embodiment in thata circuit scale of a detection chip 202 is reduced.

FIG. 12 is a circuit diagram illustrating a configuration example of apixel block 310 in the first variation of the first embodiment of thepresent technology. The pixel block 310 in the first variation of thefirst embodiment is different from that in the first embodiment in thata reset transistor 321, a floating diffusion layer 324, and a pluralityof light reception units 330 are arranged on the light reception chip201. Other elements are arranged on a detection chip 202.

In this manner, according to the first variation of the first embodimentof the present technology, since the reset transistor 321 and the likeand a plurality of light reception units 330 are arranged on the lightreception chip 201, the circuit scale of the detection chip 202 may bereduced as compared with that in the first embodiment.

[Second Variation]

In the first variation of the first embodiment described above, thereset transistor 321 and the like and the plurality of light receptionunits 330 are arranged on the light reception chip 201, but there is apossibility that the circuit scale of the detection chip 202 increasesas the number of pixels increases. A solid-state imaging element 200 ina second variation of the first embodiment is different from that in thefirst variation of the first embodiment in that a circuit scale of adetection chip 202 is further reduced.

FIG. 13 is a circuit diagram illustrating a configuration example of apixel block 310 in the second variation of the first embodiment of thepresent technology. The pixel block 310 in the second variation of thefirst embodiment is different from that in the first variation of thefirst embodiment in that N-type transistors 411 and 413 are furtherarranged on a light reception chip 201. In this manner, by using onlythe N-type transistors in the light reception chip 201, the number ofsteps of forming the transistors may be reduced as compared with a casewhere the N-type transistor and a P-type transistor are mixed.Therefore, a manufacturing cost of the light reception chip 201 may bereduced.

In this manner, according to the second variation of the firstembodiment of the present technology, since the N-type transistors 411and 413 are further arranged on the light reception chip 201, thecircuit scale of the detection chip 202 may be reduced as compared withthat in the first variation of the first embodiment.

[Third Variation]

In the second variation of the first embodiment described above, theN-type transistors 411 and 413 are further arranged on the lightreception chip 201, but there is a possibility that the circuit scale ofthe detection chip 202 increases as the number of pixels increases. Asolid-state imaging element 200 in a third variation of the firstembodiment is different from that in the second variation of the firstembodiment in that a circuit scale of a detection chip 202 is furtherreduced.

FIG. 14 is a circuit diagram illustrating a configuration example of apixel block 310 in the third variation of the first embodiment of thepresent technology. The pixel block 310 in the third variation of thefirst embodiment is different from that in the second variation of thefirst embodiment in that an amplification transistor 322 and a selectiontransistor 323 are further arranged on a light reception chip 201. Thatis, an entire pixel signal generation unit 320 is arranged on the lightreception chip 201.

In this manner, according to the third variation of the first embodimentof the present technology, since the pixel signal generation unit 320 isarranged on the light reception chip 201, the circuit scale of thedetection chip 202 may be reduced as compared with that in the secondvariation of the first embodiment.

2. Second Embodiment

Although the pixel signal generation unit 320 is provided for each pixelblock 310 in the above-described first embodiment, there is apossibility that the circuit scale of the solid-state imaging element200 increases as the number of pixels increases. A solid-state imagingelement 200 in a second embodiment is different from that in the firstembodiment in that pixel signal generation units 320 are reduced.

FIG. 15 is a block diagram illustrating a configuration example of apixel array unit 300 in the second embodiment of the present technology.The pixel array unit 300 is different from that in the first embodimentin that the pixel signal generation unit 320 is not provided.

Furthermore, an address event detection unit 400 in the secondembodiment is different from that in the first embodiment in generatinga pixel signal SIG and outputting the same via a vertical signal lineVSL.

FIG. 16 is a circuit diagram illustrating a configuration example of alight reception unit 330 in the second embodiment of the presenttechnology. The light reception unit 330 in the second embodiment isdifferent from that in the first embodiment in not including an OFGtransistor 332.

Furthermore, a transfer transistor 331 in the second embodiment suppliesa photocurrent from a photoelectric conversion element 333 to theaddress event detection unit 400 via a connection node 340.

Note that, although the transfer transistor 331 is arranged on each ofthe light reception units 330, as illustrated in FIG. 17 , it is alsopossible to adopt a configuration without the transistors provided. Inthis case, a drive circuit 211 does not need to supply a transfer signalTRGn to the light reception unit 330.

FIG. 18 is a circuit diagram illustrating a configuration example of acurrent/voltage conversion unit 410 in the second embodiment of thepresent technology. The current/voltage conversion unit 410 in thesecond embodiment is different from that in the first embodiment in thata source of an N-type transistor 413 is connected to the vertical signalline VSL.

Furthermore, when an address event is detected, the drive circuit 211lowers a voltage (V_(bias)) to a gate of a P-type transistor 412 ascompared with that before detection to a low level. Therefore, a voltageof a gate of an N-type transistor 411 reaches a power supply voltage VDDas that of a drain thereof, and the N-type transistor 411 is put into astate equivalent to a case of being diode-connected. Then, a pixelsignal SIG of a voltage corresponding to the photocurrent is generatedby the N-type transistor 413 that serves as a source follower.

Furthermore, a plurality of light reception units 330 and the N-typetransistors 411 and 413 are arranged on a light reception chip 201, andremaining elements are arranged on a detection chip 202.

FIG. 19 is a timing chart illustrating an example of an operation of thesolid-state imaging element 200 in the second embodiment of the presenttechnology.

At timing T0, when being instructed to start detecting the addressevent, the drive circuit 211 sets all transfer signals TRGn to a highlevel to turn on the transfer transistors 331 of all the pixels.

Then, suppose that the address event detection unit 400 detects theaddress event and outputs a high-level detection signal at timing T1.

Upon receiving the detection signal, the drive circuit 211 sets only atransfer signal TRG1 to a high level over a certain pulse period attiming T2. The pixel signal generation unit 320 converts a pixel signalof a first pixel into a digital signal.

At timing T3 after the conversion of the pixel signal, the drive circuit211 sets a high-level transfer signal TRG2 to a high level over acertain pulse period. The pixel signal generation unit 320 converts apixel signal of a second pixel into a digital signal. Thereafter,similar processing is executed, and the pixel signals of the respectivepixels in the pixel block 310 are sequentially output.

When all the pixel signals are output, the drive circuit 211 sets allthe transfer signals TRGn to the high level, and turns on the transfertransistors 331 of all the pixels.

In this manner, in the second embodiment of the present technology, theaddress event detection unit 400 generates the pixel signal SIG, so thatit is not necessary to arrange the pixel signal generation unit 320.Therefore, a circuit scale may be reduced as compared with that in thefirst embodiment in which the pixel signal generation unit 320 isarranged.

[Variation]

In the above-described second embodiment, an entire ADC 230 is arrangedon the detection chip 202; however, there is a possibility that thecircuit scale of the detection chip 202 increases as the number ofpixels increases. A solid-state imaging element 200 in a variation ofthe second embodiment is different from that in the second embodiment inthat a part of an ADC 230 is arranged on a light reception chip 201 toreduce a circuit scale of a detection chip 202.

FIG. 20 is a circuit diagram illustrating a configuration example of acurrent/voltage conversion unit 410 in the variation of the secondembodiment of the present technology. The current/voltage conversionunit 410 in the variation of the second embodiment is different fromthat in the second embodiment in that a source of an N-type transistor413 is grounded and a drain of an N-type transistor 411 is connected toa vertical signal line VSL. Note that, as in the second embodiment, itis also possible to connect the source of the N-type transistor 413 tothe vertical signal line VSL in place of the N-type transistor 411.

FIG. 21 is a circuit diagram illustrating a configuration example of theADC 230 in the variation of the second embodiment of the presenttechnology. The ADC 230 is provided with a differential amplificationcircuit 240 and a counter 250.

The differential amplification circuit 240 is provided with N-typetransistors 243, 244, and 245, and P-type transistors 241 and 242. Forexample, MOS transistors are used as these transistors.

The N-type transistors 243 and 244 form a differential pair, and sourcesof these transistors are commonly connected to a drain of the N-typetransistor 245. Furthermore, a drain of the N-type transistor 243 isconnected to a drain of the P-type transistor 241 and gates of theP-type transistors 241 and 242. A drain of the N-type transistor 244 isconnected to a drain of the P-type transistor 242 and the counter 250.Furthermore, a reference signal REF is input to a gate of the N-typetransistor 243, and a pixel signal SIG is input to a gate of the N-typetransistor 244 via the vertical signal line VSL. Note that, the N-typetransistor 243 is an example of a reference side transistor recited inclaims, and the N-type transistor 244 is an example of a signal sidetransistor recited in claims.

For example, a ramp signal is used as the reference signal REF. Acircuit that generates the reference signal REF is not illustrated.

A predetermined bias voltage Vb is applied to a gate of the N-typetransistor 245 and a source thereof is grounded. This N-type transistor245 supplies a constant current. Note that, the N-type transistor 245 isan example of a constant current source recited in claims.

With the above-described configuration, the P-type transistors 241 and242 form a current mirror circuit, amplify a difference between thereference signal REF and the pixel signal SIG, and output the same tothe counter 250. Then, the counter 250 counts a count value over aperiod until a signal from the differential amplification circuit 240 isinverted, and outputs a digital signal indicating the count value to thesignal processing unit 212.

Furthermore, in the variation of the second embodiment described above,the light reception chip 201 is further provided with theabove-described N-type transistors 243, 244, and 245.

In this manner, according to the variation of the second embodiment ofthe present technology, since the N-type transistors 243, 244, and 245are further arranged on the light reception chip 201, the circuit scaleof the detection chip 202 may be reduced as compared with that in thesecond embodiment.

3. Third Embodiment

In the above-described second embodiment, the capacitors 431 and 433 arearranged in the address event detection unit 400; however, the gain isdeteriorated when the capacitance C1 is reduced according to expression5, so that it is difficult to improve an operation speed of the circuitby reducing the capacitance C1. A solid-state imaging element 200according to a third embodiment is different from that in the secondembodiment in that a capacitor 431 is arranged for each pixel to improvean operation speed.

FIG. 22 is a block diagram illustrating a configuration example of apixel array unit 300 in the third embodiment of the present technology.The pixel array unit 300 in the third embodiment is different from thatin the second embodiment in that each of light reception units 330generates a pixel signal SIG in place of an address event detection unit400. Furthermore, a vertical signal line VSL is wired for each column ofpixels, for example. Then, an ADC 230 is also provided for each pixelcolumn. Note that, as in the second embodiment, the vertical signal lineVSL may be arranged for each column of pixel blocks 310 and each of thelight reception units 330 may be connected thereto. In this case, theADC 230 is also provided for each column of the pixel blocks 310.

FIG. 23 is a circuit diagram illustrating a configuration example of thelight reception unit 330 in the third embodiment of the presenttechnology. The light reception unit 330 in the third embodiment isdifferent from that in the second embodiment in further including acurrent/voltage conversion unit 410, a buffer 420, and a capacitor 431.

A circuit configuration of the current/voltage conversion unit 410 inthe third embodiment is similar to that in the variation of the secondembodiment illustrated in FIG. 19 , for example. Furthermore, anoperation of a drive circuit 211 in the third embodiment is similar tothat in the second embodiment. Furthermore, circuits and elementsarranged on a light reception chip 201 and a detection chip 202 in thethird embodiment are similar to those in the variation of the secondembodiment. That is, as illustrated in FIG. 20 , in the current/voltageconversion unit 410, N-type transistors 411 and 413 are arranged on thelight reception chip 201. Furthermore, as illustrated in FIG. 21 , inthe ADC 230, N-type transistors 243, 244, and 245 are arranged on thelight reception chip 201.

FIG. 24 is a block diagram illustrating a configuration example of theaddress event detection unit 400 in the third embodiment of the presenttechnology. The address event detection unit 400 in the third embodimentis different from that in the second embodiment in not including thecurrent/voltage conversion unit 410, the buffer 420, and the capacitor431.

As described above, in the third embodiment, unlike the secondembodiment in which a plurality of light reception units 330 connectedin parallel shares one capacitor 431, the capacitor 431 is provided foreach light reception unit 330. For this reason, individual capacitanceof the capacitor 431 may be (C1)/N when the number of light receptionunits 330 (that is, the number of pixels) is set to N. By this reductionin capacitance, the operating speed of the circuit may be improved.However, an overall gain A in the third embodiment is expressed by afollowing expression.

[Mathematical Expression 2]

$\begin{matrix}{A = {{\frac{{{CG}_{\log} \cdot C}1}{{N \cdot C}2}{\sum\limits_{n = 1}^{N}i_{photo}}} - n}} & {{Expression}7}\end{matrix}$

From Expressions 6 and 7, the gain A in the third embodiment is smallerthan that in the first and second embodiments. For this reason, inexchange for improvement in operation speed, detection accuracy of theaddress event decreases.

In this manner, according to the third embodiment of the presenttechnology, since the capacitor 431 is arranged for each of the lightreception units 330, it is possible to improve the operation speed ofthe circuit including the capacitor 431 as compared with a case where aplurality of light reception units 330 shares the capacitor 431.

[Variation]

In the above-described third embodiment, the plurality of lightreception units 330 (pixels) in the column shares one ADC 230, but sinceit is required to sequentially convert the pixel signals of those pixelsinto digital signals, a read speed of the pixel signals decreases as thenumber of pixels in the column increases. A solid-state imaging element200 in a variation of the third embodiment is different from that in thethird embodiment in that an ADC 230 is arranged for each pixel.

FIG. 25 is a circuit diagram illustrating a configuration example of alight reception unit 330 in the variation of the third embodiment of thepresent technology. The light reception unit 330 in the variation of thethird embodiment is different from that in the third embodiment infurther including the ADC 230.

In this manner, according to the variation of the third embodiment ofthe present technology, since the ADC 230 is arranged for each of thelight reception units 330, it is possible to improve a read speed of apixel signal as compared with a configuration in which a plurality oflight reception units 330 shares one ADC 230.

4. Fourth Embodiment

In the above-described first embodiment, the address event is detectedfor each pixel block 310 including a plurality of pixels, but it is notpossible to detect the address event occurring in each pixel. Asolid-state imaging element 200 in a fourth embodiment is different fromthat in the first embodiment in that an address event detection unit 400is arranged for each pixel.

FIG. 26 is a block diagram illustrating a configuration example of apixel array unit 300 in the fourth embodiment of the present technology.The pixel array unit 300 in the fourth embodiment is different from thatin the first embodiment in that a plurality of pixels 311 is arranged ina two-dimensional lattice manner. A pixel signal generation unit 320, alight reception unit 330, and the address event detection unit 400 arearranged in each of the pixels 311. Circuit configurations of the pixelsignal generation unit 320, the light reception unit 330, and theaddress event detection unit 400 are similar to those in the firstembodiment.

Furthermore, circuits and elements arranged in the light reception chip201 and the detection chip 202 are similar to those in any of the firstembodiment and the first, second, and third variations of the firstembodiment. For example, as illustrated in FIG. 5 , only a photoelectricconversion element 333 is arranged on a light reception chip 201, andremaining elements are arranged on a detection chip 202.

In this manner, according to the fourth embodiment of the presenttechnology, since the address event detection unit 400 is arranged foreach pixel, the address event may be detected for each pixel. Therefore,resolution of detection data of the address event may be improved ascompared with a case where the address event is detected for each pixelblock 310.

[Variation]

Although the address event detection unit 400 is arranged in all thepixels in the above-described fourth embodiment, it is possible that thecircuit scale of the solid-state imaging element 200 increases as thenumber of pixels increases. A solid-state imaging element 200 in avariation of the fourth embodiment is different from that in the fourthembodiment in that an address event detection unit 400 is arranged onlyin a pixel being a detection target out of a plurality of pixels.

FIG. 27 is a block diagram illustrating a configuration example of apixel array unit 300 in the variation of the fourth embodiment of thepresent technology. The pixel array unit 300 in the variation of thefourth embodiment is different from that in the fourth embodiment inthat a pixel in which the address event detection unit 400 is notarranged and a pixel in which the address event detection unit 400 isarranged are arranged. The former is a normal pixel 312 and the latteris an address event detection pixel 313. The address event detectionpixels 313 are arranged at regular intervals, for example. Note that, aplurality of address event detection pixels 313 may be arranged so as tobe adjacent to each other.

Furthermore, a configuration of the address event detection pixel 313 issimilar to that of the pixel 311 in the fourth embodiment. The normalpixel 312 is described later in detail.

FIG. 28 is a circuit diagram illustrating a configuration example of thenormal pixel 312 in the variation of the fourth embodiment of thepresent technology. The normal pixel 312 in the variation of the fourthembodiment is provided with a photoelectric conversion element 333, atransfer transistor 331, a reset transistor 321, an amplificationtransistor 322, a selection transistor 323, and a floating diffusionlayer 324. A connection configuration of these elements is similar tothat in the first embodiment illustrated in FIG. 5 .

In this manner, according to the variation of the fourth embodiment ofthe present technology, since the address event detection unit 400 isarranged only in the address event detection pixel 313 among all thepixels, a circuit scale may be reduced as compared with theconfiguration in which the address event detection unit 400 is arrangedin all the pixels.

5. Fifth Embodiment

In the first embodiment described above, the number of pixels sharingthe address event detection unit 400 and the number of pixels sharingthe image signal generation unit 320 are made the same, but the lattermay be reduced. A solid-state imaging element 200 in a fifth embodimentis different from that in the first embodiment in that the number ofpixels sharing an image signal generation unit 320 is smaller than thenumber of pixels sharing an address event detection unit 400.

FIG. 29 is a block diagram illustrating a configuration example of apixel array unit 300 in the fifth embodiment of the present technology.In the pixel array unit 300 in the fifth embodiment, N light receptionunits 330 (pixels) and one address event detection unit 400 are arrangedin each of pixel blocks 310. Furthermore, in each of the pixel blocks310, the pixel signal generation unit 320 is arranged for every M (M isan integer smaller than N) light reception units 330 (pixels).

FIG. 30 is a block diagram illustrating a configuration example of thepixel block 310 in the fifth embodiment of the present technology. Ineach of the pixel blocks 310, the N light reception units 330 (pixels)share one address event detection unit 400. Furthermore, the M pixelsshare one image signal generation unit 320. The image signal generationunit 320 generates the pixel signal of a selected pixel out of thecorresponding M pixels.

In this manner, according to the fifth embodiment of the presenttechnology, the number of pixels sharing the image signal generationunit 320 is made smaller than the number of pixels sharing the addressevent detection unit 400, so that it is possible to improve a read speedof a pixel signal as compared with a case where they made the same.

6. Sixth Embodiment

In the first embodiment described above, a plurality of pixels sharesthe image signal generation unit 320 and the address event detectionunit 400; however, it is also possible to arrange the address eventdetection unit 400 for each pixel. A solid-state imaging element 200 ina sixth embodiment is different from that in the first embodiment inthat an address event detection unit 400 is arranged for each pixelwhile a plurality of pixels shares an image signal generation unit 320.

FIG. 31 is a block diagram illustrating a configuration example of apixel block 310 in the sixth embodiment of the present technology. Ineach of the pixel blocks 310, the N light reception units 330 (pixels)share one pixel signal generation unit 320. On the other hand, theaddress event detection unit 400 is arranged for each light receptionunit 330 (pixel), and the light reception unit 330 is connected to acorresponding address event detection unit 400.

In this manner, according to the sixth embodiment of the presenttechnology, since the address event detection unit 400 is arranged foreach pixel, presence/absence of an address event may be detected foreach pixel.

7. Application Example to Mobile Body

The technology according to the present disclosure (present technology)is applicable to various products. For example, the technology accordingto the present disclosure may also be realized as a device mounted onany type of mobile body such as an automobile, an electric automobile, ahybrid electric automobile, a motorcycle, a bicycle, a personalmobility, an airplane, a drone, a ship, and a robot.

FIG. 32 is a block diagram illustrating a schematic configurationexample of a vehicle control system that is an example of a mobile bodycontrol system to which the technology according to the presentdisclosure may be applied.

A vehicle control system 12000 is provided with a plurality ofelectronic control units connected to one another via a communicationnetwork 12001. In the example illustrated in FIG. 32 , the vehiclecontrol system 12000 is provided with a drive system control unit 12010,a body system control unit 12020, a vehicle exterior informationdetection unit 12030, a vehicle interior information detection unit12040, and an integrated control unit 12050. Furthermore, amicrocomputer 12051, an audio image output unit 12052, and an in-vehiclenetwork interface (I/F) 12053 are illustrated as functionalconfigurations of the integrated control unit 12050.

The drive system control unit 12010 controls operation of devicesrelated to a drive system of a vehicle according to various programs.For example, the drive system control unit 12010 serves as a controldevice of a driving force generating device for generating driving forceof the vehicle such as an internal combustion engine or a driving motor,a driving force transmitting mechanism for transmitting the drivingforce to wheels, a steering mechanism for adjusting a rudder angle ofthe vehicle, a braking device for generating braking force of thevehicle and the like.

The body system control unit 12020 controls operation of various devicesmounted on a vehicle body in accordance with the various programs. Forexample, the body system control unit 12020 serves as a control deviceof a keyless entry system, a smart key system, a power window device, orvarious lights such as a head light, a backing light, a brake light, ablinker, or a fog light. In this case, a radio wave transmitted from aportable device that substitutes for a key or signals of variousswitches may be input to the body system control unit 12020. The bodysystem control unit 12020 receives an input of the radio wave or signalsand controls a door lock device, a power window device, the lights andthe like of the vehicle.

The vehicle exterior information detection unit 12030 detectsinformation outside the vehicle on which the vehicle control system12000 is mounted. For example, an imaging unit 12031 is connected to thevehicle exterior information detection unit 12030. The vehicle exteriorinformation detection unit 12030 allows the imaging unit 12031 to takean image of the exterior of the vehicle and receives the taken image.The vehicle exterior information detection unit 12030 may performdetection processing of objects such as a person, a vehicle, anobstacle, a sign, or a character on a road surface or distance detectionprocessing on the basis of the received image.

The imaging unit 12031 is an optical sensor that receives light andoutputs an electric signal corresponding to an amount of the receivedlight. The imaging unit 12031 may output the electric signal as theimage or output the same as ranging information. Furthermore, the lightreceived by the imaging unit 12031 may be visible light or invisiblelight such as infrared light.

The vehicle interior information detection unit 12040 detectsinformation in the vehicle. The vehicle interior information detectionunit 12040 is connected to, for example, a driver state detection unit12041 for detecting a state of a driver. The driver state detection unit12041 includes, for example, a camera that images the driver, and thevehicle interior information detection unit 12040 may calculate adriver's fatigue level or concentration level or may determine whetheror not the driver is dozing on the basis of detection information inputfrom the driver state detection unit 12041.

The microcomputer 12051 may calculate a control target value of thedriving force generating device, the steering mechanism, or the brakingdevice on the basis of the information inside and outside the vehicleobtained by the vehicle exterior information detection unit 12030 or thevehicle interior information detection unit 12040, and output a controlinstruction to the drive system control unit 12010. For example, themicrocomputer 12051 may perform cooperative control for realizingfunctions of advanced driver assistance system (ADAS) includingcollision avoidance or impact attenuation of the vehicle, followingtravel based on the distance between the vehicles, vehicle speedmaintaining travel, vehicle collision warning, vehicle lane departurewarning and the like.

Furthermore, the microcomputer 12051 may perform the cooperative controlfor realizing automatic driving and the like to autonomously travelindependent from the operation of the driver by controlling the drivingforce generating device, the steering mechanism, the braking device andthe like on the basis of the information around the vehicle obtained bythe vehicle exterior information detection unit 12030 or the vehicleinterior information detection unit 12040.

Furthermore, the microcomputer 12051 may output the control instructionto the body system control unit 12020 on the basis of the informationoutside the vehicle obtained by the vehicle exterior informationdetection unit 12030. For example, the microcomputer 12051 may performthe cooperative control to realize glare protection such as controllingthe head light according to a position of a preceding vehicle or anoncoming vehicle detected by the vehicle exterior information detectionunit 12030 to switch a high beam to a low beam.

The audio image output unit 12052 transmits at least one of audio orimage output signal to an output device capable of visually or audiblynotifying an occupant of the vehicle or the outside the vehicle of theinformation. In the example in FIG. 32 , as the output device, an audiospeaker 12061, a display unit 12062, and an instrument panel 12063 areillustrated. The display unit 12062 may include at least one of anon-board display or a head-up display, for example.

FIG. 33 is a view illustrating an example of an installation position ofthe imaging unit 12031.

In FIG. 33 , imaging units 12101, 12102, 12103, 12104, and 12105 areincluded as the imaging unit 12031.

The imaging units 12101, 12102, 12103, 12104, and 12105 are provided inpositions such as, for example, a front nose, a side mirror, a rearbumper, a rear door, and an upper portion of a front windshield in avehicle interior of the vehicle 12100. The imaging unit 12101 providedon the front nose and the imaging unit 12105 provided in the upperportion of the front windshield in the vehicle interior principallyobtain images in front of the vehicle 12100. The imaging units 12102 and12103 provided on the side mirrors principally obtain images of thesides of the vehicle 12100. The imaging unit 12104 provided on the rearbumper or the rear door principally obtains an image behind the vehicle12100. The imaging unit 12105 provided on the upper portion of the frontwindshield in the vehicle interior is mainly used for detecting thepreceding vehicle, a pedestrian, an obstacle, a traffic signal, atraffic sign, a lane and the like.

Note that, in FIG. 33 , an example of imaging ranges of the imagingunits 12101 to 12104 is illustrated. An imaging range 12111 indicatesthe imaging range of the imaging unit 12101 provided on the front nose,imaging ranges 12112 and 12113 indicate the imaging ranges of theimaging units 12102 and 12103 provided on the side mirrors, and animaging range 12114 indicates the imaging range of the imaging unit12104 provided on the rear bumper or the rear door. For example, imagedata taken by the imaging units 12101 to 12104 are superimposed, so thatan overlooking image of the vehicle 12100 as seen from above isobtained.

At least one of the imaging units 12101 to 12104 may have a function ofobtaining distance information. For example, at least one of the imagingunits 12101 to 12104 may be a stereo camera including a plurality ofimaging elements, or may be an imaging element including pixels forphase difference detection.

For example, the microcomputer 12051 may extract especially a closestsolid object on a traveling path of the vehicle 12100, the solid objecttraveling at a predetermined speed (for example, 0 km/h or higher) in adirection substantially the same as that of the vehicle 12100 as thepreceding vehicle by obtaining a distance to each solid object in theimaging ranges 12111 to 12114 and a change in time of the distance(relative speed relative to the vehicle 12100) on the basis of thedistance information obtained from the imaging units 12101 to 12104.Moreover, the microcomputer 12051 may set the distance between thevehicles to be secured in advance from the preceding vehicle, and mayperform automatic brake control (including following stop control),automatic acceleration control (including following start control) andthe like. In this manner, it is possible to perform the cooperativecontrol for realizing the automatic driving and the like to autonomouslytravel independent from the operation of the driver.

For example, the microcomputer 12051 may extract solid object dataregarding the solid object while sorting the same into a motorcycle, astandard vehicle, a large-sized vehicle, a pedestrian, and other solidobjects such as a utility pole on the basis of the distance informationobtained from the imaging units 12101 to 12104 and use for automaticallyavoiding obstacles. For example, the microcomputer 12051 discriminatesthe obstacles around the vehicle 12100 into an obstacle visible to adriver of the vehicle 12100 and an obstacle difficult to see. Then, themicrocomputer 12051 determines a collision risk indicating a degree ofrisk of collision with each obstacle, and when the collision risk isequal to or higher than a set value and there is a possibility ofcollision, this may perform driving assistance for avoiding thecollision by outputting an alarm to the driver via the audio speaker12061 and the display unit 12062 or performing forced deceleration oravoidance steering via the drive system control unit 12010.

At least one of the imaging units 12101 to 12104 may be an infraredcamera for detecting infrared rays. For example, the microcomputer 12051may recognize a pedestrian by determining whether or not there is apedestrian in the images taken by the imaging units 12101 to 12104. Suchpedestrian recognition is carried out, for example, by a procedure ofextracting feature points in the images taken by the imaging units 12101to 12104 as the infrared cameras and a procedure of performing patternmatching processing on a series of feature points indicating an outlineof an object to discriminate whether or not this is a pedestrian. Whenthe microcomputer 12051 determines that there is a pedestrian in theimages taken by the imaging units 12101 to 12104 and recognizes thepedestrian, the audio image output unit 12052 controls the display unit12062 to superimpose a rectangular contour for emphasis on therecognized pedestrian. Furthermore, the audio image output unit 12052may control the display unit 12062 to display an icon and the likeindicating the pedestrian at a desired position.

An example of the vehicle control system to which the technologyaccording to the present disclosure may be applied is described above.The technology according to the present disclosure may be applied to theimaging unit 12031, for example, out of the configurations describedabove. Specifically, the imaging device 100 in FIG. 1 may be applied tothe imaging unit 12031. By applying the technology according to thepresent disclosure to the imaging unit 12031, it is possible to reducethe circuit mounting area and downsize the imaging unit 12031.

Note that, the above-described embodiments describe an example ofembodying the present technology, and there is a correspondencerelationship between matters in the embodiments and the mattersspecifying the invention in claims. Similarly, there is a correspondencerelationship between the matters specifying the invention in claims andthe matters in the embodiments of the present technology assigned withthe same names. However, the present technology is not limited to theembodiments and may be embodied with various modifications of theembodiment without departing from the spirit thereof.

Furthermore, the procedures described in the above-described embodimentsmay be considered as a method including a series of procedures and maybe considered as a program for allowing a computer to execute the seriesof procedures and a recording medium which stores the program. A compactdisc (CD), a MiniDisc (MD), a digital versatile disc (DVD), a memorycard, a Blu-ray™ Disc and the like may be used, for example, as therecording medium.

Note that, the effect described in this specification is illustrativeonly and is not limitative; there may also be another effect.

Note that, the present technology may also have a followingconfiguration.

(1) A solid-state imaging element provided with:

-   -   a plurality of photoelectric conversion elements each of which        photoelectrically converts incident light to generate a first        electric signal; and    -   a detection unit that detects whether or not a change amount of        the first electric signal of each of the plurality of        photoelectric conversion elements exceeds a predetermined        threshold and outputs a detection signal indicating a result of        the detection.

(2) The solid-state imaging element according to (1) described above,further provided with:

-   -   a signal supply unit that supplies the first electric signal of        each of the plurality of photoelectric conversion elements to a        connection node according to a predetermined control signal,    -   in which the detection unit detects whether or not the change        amount of the first electric signal supplied to the connection        node exceeds the predetermined threshold.

(3) The solid-state imaging element according to (2) described above,further provided with:

-   -   a pixel signal generation unit that generates a pixel signal        according to a second electric signal generated by the        photoelectric conversion element,    -   in which the signal supply unit sequentially selects the second        electric signal of each of the plurality of photoelectric        conversion elements to supply to the pixel signal generation        unit in a case where the change amount exceeds the predetermined        threshold.

(4) The solid-state imaging element according to (3) described above,

-   -   in which the connection node is connected to N (N is an integer        not smaller than 2) of the photoelectric conversion elements,        and    -   the pixel signal generation unit generates a signal of a voltage        corresponding to the second electric signal of an element        selected according to a selection signal out of M (M is an        integer smaller than N) of the photoelectric conversion elements        as the pixel signal.

(5) The solid-state imaging element according to (3) described above,

-   -   in which the pixel signal generation unit is provided with:    -   a reset transistor that initializes a floating diffusion layer;    -   an amplification transistor that amplifies a signal of a voltage        of the floating diffusion layer; and    -   a selection transistor that outputs the amplified signal as the        pixel signal according to a selection signal, and    -   the detection unit is provided with:    -   a plurality of N-type transistors that converts the first        electric signal into a voltage signal of a logarithm of the        first electric signal; and    -   a P-type transistor that supplies a constant current to the        plurality of N-type transistors.

(6) The solid-state imaging element according to (5) described above,

-   -   in which the plurality of photoelectric conversion elements is        arranged on a light reception chip, and    -   the detection unit and the pixel signal generation unit are        arranged on a detection chip stacked on the light reception        chip.

(7) The solid-state imaging element according to (5) described above,

-   -   in which the plurality of photoelectric conversion elements and        the reset transistor are arranged on a light reception chip, and    -   the detection unit, the amplification transistor, and the        selection transistor are arranged on a detection chip stacked on        the light reception chip.

(8) The solid-state imaging element according to (5) described above,

-   -   in which the plurality of photoelectric conversion elements, the        reset transistor, and the plurality of N-type transistors are        arranged on a light reception chip, and    -   the amplification transistor, the selection transistor, and the        P-type transistor are arranged on a detection chip stacked on        the light reception chip.

(9) The solid-state imaging element according to (5) described above,

-   -   in which the plurality of photoelectric conversion elements, the        pixel signal generation unit, and the plurality of N-type        transistors are arranged on a light reception chip, and    -   the P-type transistor is arranged on a detection chip stacked on        the light reception chip.

(10) The solid-state imaging element according to (1) described above,further provided with:

-   -   a signal supply unit that supplies the first electric signal of        each of the plurality of photoelectric conversion elements to a        connection node according to a predetermined control signal,    -   in which the detection unit further outputs a pixel signal        corresponding to the first electric signal,    -   the signal supply unit sequentially selects the first electric        signal of each of the plurality of photoelectric conversion        elements to supply to the connection node in a case where the        change amount exceeds the predetermined threshold, and    -   the detection unit is provided with:    -   first and second N-type transistors that convert the first        electric signal into a voltage signal of a logarithm of the        first electric signal; and    -   a P-type transistor that supplies a constant current to the        first and second N-type transistors.

(11) The solid-state imaging element according to (10) described above,further provided with:

-   -   an analog/digital converter that converts the pixel signal into        a digital signal,    -   in which the plurality of photoelectric conversion elements, the        signal supply unit, and the first and second N-type transistors        are arranged on a light reception chip, and    -   the P-type transistor and at least a part of the analog/digital        converter are arranged on a detection chip stacked on the light        reception chip.

(12) The solid-state imaging element according to (11) described above,

-   -   in which the analog/digital converter is provided with:    -   a signal side transistor to which the pixel signal is input;    -   a reference side transistor to which a predetermined reference        signal is input;    -   a constant current source connected to the signal side        transistor and the reference side transistor; and    -   a current mirror circuit that amplifies a difference between the        pixel signal and the predetermined reference signal to output,    -   the plurality of photoelectric conversion elements, the signal        supply unit, the first and second N-type transistors, the signal        side transistor, the reference side transistor, and the constant        current source are arranged on a light reception chip, and    -   the P-type transistor and the current mirror circuit are        arranged on a detection chip stacked on the light reception        chip.

(13) The solid-state imaging element according to (1) described above,further provided with:

-   -   a connection node connected to the photoelectric conversion        element and the detection unit; and    -   for each of the plurality of photoelectric conversion elements,        a current/voltage conversion unit that converts a photocurrent        into a voltage signal of a logarithm of the photocurrent, a        buffer that corrects the voltage signal to output, a capacitor        inserted between the buffer and the connection node, and a        signal processing unit that supplies an electric signal of each        of the plurality of photoelectric conversion elements to the        connection node through the current/voltage conversion unit, the        buffer, and the capacitor according to a predetermined control        signal,    -   in which the electric signal includes the photocurrent and the        voltage signal.

(14) The solid-state imaging element according to (13) described above,further provided with:

-   -   an analog/digital converter that converts a pixel signal into a        digital signal,    -   in which each of a predetermined number of current/voltage        conversion units arranged in a predetermined direction further        generates a signal of a voltage corresponding to the        photocurrent as the pixel signal, and outputs the pixel signal        to the analog/digital converter.

(15) The solid-state imaging element according to (13) described above,further provided with:

-   -   an analog/digital converter that converts a pixel signal into a        digital signal for each of the plurality of photoelectric        conversion elements,    -   in which each of current/voltage conversion units further        generates a signal of a voltage corresponding to the        photocurrent as the pixel signal, and outputs the pixel signal        to the analog/digital converter.

(16) A solid-state imaging element provided with:

-   -   a photoelectric conversion element that photoelectrically        converts incident light to generate an electric signal;    -   a signal supply unit that supplies the electric signal to either        a connection node or a floating diffusion layer according to a        predetermined control signal;    -   a detection unit that detects whether or not a change amount of        the electric signal supplied to the connection node exceeds a        predetermined threshold and outputs a detection signal        indicating a result of the detection; and    -   a pixel signal generation unit that generates a voltage signal        corresponding to the electric signal supplied to the floating        diffusion layer as a pixel signal.

(17) The solid-state imaging element according to (16) described above,

-   -   in which the signal supply unit includes:    -   a first transistor that supplies the electric signal to the        connection node according to a predetermined control signal; and    -   a second transistor that supplies the electric signal to a        floating diffusion layer according to a predetermined control        signal,    -   the pixel signal generation unit is arranged in each of a        plurality of pixels, and    -   the first transistor and the detection unit are arranged in a        pixel being a detection target out of the plurality of pixels.

(18) An imaging device provided with:

-   -   a plurality of photoelectric conversion elements each of which        photoelectrically converts incident light to generate an        electric signal;    -   a signal supply unit that supplies the electric signal of each        of the plurality of photoelectric conversion elements to a        connection node according to a predetermined control signal;    -   a detection unit that detects whether or not a change amount of        the electric signal supplied to the connection node exceeds a        predetermined threshold and outputs a detection signal        indicating a result of the detection; and    -   a recording unit that records the detection signal.

(19) A control method of a solid-state imaging element, the methodprovided with:

-   -   a signal supplying step of supplying, to a connection node, an        electric signal of each of a plurality of photoelectric        conversion elements each of which photoelectrically converts        incident light to generate the electric signal according to a        predetermined control signal; and    -   a detecting step of detecting whether or not a change amount of        the electric signal supplied to the connection node exceeds a        predetermined threshold and outputting a detection signal        indicating a result of the detection.

(20) A solid-state imaging element provided with:

-   -   a first photoelectric conversion element that generates a first        electric signal;    -   a second photoelectric conversion element that generates a        second electric signal;    -   a detection unit that detects whether or not at least any one of        a change amount of the first electric signal or a change amount        of the second electric signal exceeds a predetermined threshold        to output a detection signal indicating a result of the        detection; and    -   a connection node connected to the first photoelectric        conversion element, the second photoelectric conversion element,        and the detection unit.

(21) The solid-state imaging element according to (20) described above,further provided with:

-   -   a first transistor that supplies the first electric signal to        the connection node according to a first control signal; and    -   a second transistor that supplies the second electric signal to        the connection node according to a second control signal,    -   in which the detection unit detects whether or not a change        amount of either the first or second electric signal supplied to        the connection node exceeds the predetermined threshold.

(22) The solid-state imaging element according to (21) described above,further provided with:

-   -   a pixel signal generating unit that generates a first pixel        signal according to a third electric signal generated by the        first photoelectric conversion element and generates a second        pixel signal according to a fourth electric signal generated by        the second photoelectric conversion element;    -   a third transistor connected to the first photoelectric        conversion element and the pixel signal generating unit; and    -   a fourth transistor connected to the second photoelectric        conversion element and the pixel signal generating unit,    -   in which the third transistor supplies the third electric signal        to the pixel signal generating unit in a case where the change        amount of the first electric signal exceeds the predetermined        threshold, and    -   the fourth transistor supplies the fourth electric signal to the        pixel signal generating unit in a case where the change amount        of the second electric signal exceeds the predetermined        threshold (23) The solid-state imaging element according to (22)        described above,    -   in which the pixel signal generating unit includes:    -   a first pixel signal generation unit that generates a first        pixel signal according to the third electric signal generated by        the first photoelectric conversion element; and    -   a second pixel signal generation unit that generates a second        pixel signal according to the fourth electric signal generated        by the second photoelectric conversion element,    -   the third transistor supplies the third electric signal to the        first pixel signal generation unit in a case where the change        amount of the first electric signal exceeds the predetermined        threshold, and    -   the fourth transistor supplies the fourth electric signal to the        second pixel signal generation unit in a case where the change        amount of the second electric signal exceeds the predetermined        threshold (24) The solid-state imaging element according to (22)        described above, further provided with:    -   a third photoelectric conversion element that generates a fifth        electric signal and a sixth electric signal;    -   a fifth transistor that supplies an electric signal of the fifth        photoelectric conversion element to the connection node        according to a third control signal; and    -   a second pixel signal generating unit that generates a third        pixel signal according to the sixth electric signal,    -   in which the sixth transistor supplies the sixth electric signal        to the second pixel signal generating unit in a case where a        change amount of the fifth electric signal exceeds the        predetermined threshold.

(25) The solid-state imaging element according to (22) described above,

-   -   in which the pixel signal generating unit is provided with:    -   a reset transistor that initializes a floating diffusion layer;    -   an amplification transistor that amplifies a signal of a voltage        of the floating diffusion layer; and    -   a selection transistor that outputs the amplified signal as the        first or second pixel signal according to a selection signal,        and    -   the detection unit is provided with:    -   a plurality of N-type transistors that converts a photocurrent        into a voltage signal of a logarithm of the photocurrent; and    -   a P-type transistor that supplies a constant current to the        plurality of N-type transistors.

(26) The solid-state imaging element according to (20) described above,

-   -   the first electric signal including a first photocurrent, and    -   the second electric signal including a second photocurrent,    -   the solid-state imaging element further provided with:    -   a connection node connected to the first photoelectric        conversion element, the second photoelectric conversion element,        and the detection unit;    -   a first current/voltage conversion unit that converts at least        one of the first photocurrent or the second photocurrent into a        voltage signal of a logarithm of the photocurrent;    -   a buffer that corrects the voltage signal to output;    -   a capacitor inserted between the buffer and the connection node;        and    -   a signal processing unit that supplies at least one of the first        electric signal or the second electric signal to the connection        node through the current/voltage conversion unit, the buffer,        and the capacitor according to a predetermined control signal,    -   in which the first photoelectric conversion element generates        the first photocurrent, and    -   the second photoelectric conversion element generates the second        photocurrent. (27) The solid-state imaging element according        to (26) described above, further provided with:    -   an analog/digital converter connected to the first        current/voltage conversion unit and the second current/voltage        conversion unit,    -   in which the first current/voltage conversion unit further        generates a signal of a voltage corresponding to the first        photocurrent as a first pixel signal, and outputs the first        pixel signal to the analog/digital converter, and    -   the second current/voltage conversion unit further generates a        signal of a voltage corresponding to the second photocurrent as        a second pixel signal, and outputs the second pixel signal to        the analog/digital converter.

(28) The solid-state imaging element according to (26) described above,further provided with:

-   -   a first analog/digital converter that converts a first pixel        signal into a first digital signal; and    -   a second analog/digital converter that converts a second pixel        signal into a second digital signal,    -   in which the first current/voltage conversion unit further        generates a signal of a voltage corresponding to the first        photocurrent as the first pixel signal, and outputs the first        pixel signal to the first analog/digital converter, and    -   the second current/voltage conversion unit further generates a        signal of a voltage corresponding to the second photocurrent as        the second pixel signal, and outputs the second pixel signal to        the second analog/digital converter.

(29) A solid-state imaging element provided with:

-   -   a first photoelectric conversion element that photoelectrically        converts incident light to generate a first electric signal and        a second electric signal;    -   a first signal supply unit that supplies the first electric        signal to a connection node according to a first control signal;    -   a second signal supply unit that supplies the second electric        signal to a first floating diffusion layer according to a second        control signal;    -   a detection unit that detects whether or not a change amount of        the first electric signal supplied to the connection node        exceeds a predetermined threshold and outputs a detection signal        indicating a result of the detection; and    -   a first pixel signal generation unit that generates a first        pixel signal corresponding to the second electric signal        supplied to the first floating diffusion layer.

(30) The solid-state imaging element according to (29) described above,further provided with:

-   -   a second photoelectric conversion element that photoelectrically        converts incident light to generate a third electric signal;    -   a third transistor that supplies to a second floating diffusion        layer according to a third control signal; and    -   a second pixel signal generation unit that generates a voltage        signal corresponding to the third electric signal supplied to        the second floating diffusion layer as a second pixel signal.

(31) An imaging device provided with:

-   -   a first photoelectric conversion element that photoelectrically        converts incident light to generate a first electric signal;    -   a second photoelectric conversion element that photoelectrically        converts the incident light to generate a second electric        signal;    -   a first signal supply unit that supplies the first electric        signal to a connection node according to a first control signal;    -   a second signal supply unit that supplies the second electric        signal to the connection node according to a second control        signal;    -   a detection unit that detects whether or not a change amount of        the electric signal supplied to the connection node exceeds a        predetermined threshold and outputs a detection signal        indicating a result of the detection; and    -   a recording unit that records the detection signal.

(32) A control method of a solid-state imaging element, the methodprovided with:

-   -   a signal supplying step of supplying a first electric signal        generated by photoelectric conversion of incident light by a        first photoelectric conversion element to a connection node        according to a first control signal and supplying a second        electric signal generated by photoelectric conversion of the        incident light by a second photoelectric conversion element to        the connection node according to a second control signal; and    -   a detecting step of detecting whether or not a change amount of        the electric signal supplied to the connection node exceeds a        predetermined threshold and outputting a detection signal        indicating a result of the detection.

(33) A solid-state imaging element provided with:

-   -   a first photoelectric conversion element that photoelectrically        converts incident light to generate first and second electric        signals;    -   a second photoelectric conversion element that photoelectrically        converts the incident light to generate third and fourth        electric signals;    -   a first detection unit that detects whether or not a change        amount of the first electric signal exceeds a predetermined        threshold and outputs a detection signal indicating a result of        the detection;    -   a second detection unit that detects whether or not a change        amount of the third electric signal exceeds a predetermined        threshold and outputs a detection signal indicating a result of        the detection;    -   a first transistor that supplies the first electric signal to        the first detection unit according to a first control signal;    -   a second transistor that supplies the third electric signal to        the second detection unit according to a second control signal;    -   a pixel signal generation unit that generates a pixel signal        corresponding to any one of the second or fourth pixel signal;    -   a third transistor that supplies the second electric signal to        the pixel signal generation unit according to a third control        signal; and    -   a fourth transistor that supplies the fourth electric signal to        the pixel signal generation unit according to a fourth control        signal.

REFERENCE SIGNS LIST

-   100 Imaging device-   110 Imaging lens-   120 Recording unit-   130 Control unit-   200 Solid-state imaging element-   201 Light reception chip-   202 Detection chip-   211 Drive circuit-   212 Signal processing unit-   213 Arbiter-   220 Column ADC-   221 Reference signal generation unit-   222 Output unit-   230 ADC-   231 Comparator-   232 Counter-   233 Switch-   234 Memory-   240 Differential amplification circuit-   241, 242, 412 P-type transistor-   243, 244, 245, 411, 413N-type transistor-   250 Counter-   300 Pixel array unit-   310 Pixel block-   311 Pixel-   312 Normal pixel-   313 Address event detection pixel-   320 Pixel signal generation unit-   321 Reset transistor-   322 Amplification transistor-   323 Selection transistor-   324 Floating diffusion layer-   330 Light reception unit-   331 Transfer transistor-   332 OFG transistor-   333 Photoelectric conversion element-   400 Address event detection unit-   410 Current/voltage conversion unit-   420 Buffer-   430 Subtractor-   431, 433 Capacitor-   432 Inverter-   434 Switch-   440 Quantizer-   441 Comparator-   450 Transfer unit-   12031 Imaging unit

The invention claimed is:
 1. A light detection device comprising: afirst semiconductor substrate including a photoelectric conversionelement, a transfer transistor coupled to the photoelectric conversionelement, a floating diffusion coupled to the transfer transistor, anamplification transistor coupled to the floating diffusion, and aselection transistor coupled to the amplification transistor; and asecond semiconductor substrate including an event detection circuitrythat includes at least a portion of current/voltage conversion circuitrythat outputs a first pixel signal based on an output of thephotoelectric conversion element, and a quantizer that outputs a firstdigital signal based on the first pixel signal, wherein, an analog todigital conversion circuitry receives a second pixel signal based on anoutput of the photoelectric conversion element via the selectiontransistor, and converts the second pixel signal to a second digitalsignal.
 2. The light detection device according to claim 1, wherein thefirst pixel signal is supplied to a connection node, and the eventdetection circuitry is configured to detect whether a change amount ofthe first pixel signal exceeds a predetermined threshold.
 3. The lightdetection device according to claim 2, wherein the second pixel signalis selected via the selection transistor when the change amount of thefirst pixel signal exceeds the predetermined threshold.
 4. The lightdetection device according to claim 1, wherein the first semiconductorsubstrate is arranged on a first chip, and the second semiconductorsubstrate is arranged on a second chip stacked on the first chip.
 5. Thelight detection device according to claim 1, wherein the photoelectricconversion element is arranged on a first chip, and the event detectioncircuitry is arranged on a second chip stacked on the first chip.
 6. Thelight detection device according to claim 5, wherein the analog todigital conversion circuitry is arranged on the second chip.
 7. Thesolid-state imaging element according to claim 1, wherein thecurrent/voltage conversion circuitry is configured to convert aphotocurrent based on the output of the photoelectric conversion elementinto a voltage signal of a logarithm of the photocurrent.